EFFECT OF LASER-PULSES ON THE PHOTOELECTRON EMISSION FROM NA-((C222)NA)

Photoemission from crystalline Na+(C222Na- has been measured from 240 to 900 nm. Pure sodium cryptand sodide crystals have an emission peak at approximate to 290 nm (approximate to 4.3 eV) and a very low emissi on on the low-energy side above 400 nm. The photoemission threshold of this sodide is approximate to 3.1 eV. Most crystalline samples contai n, however, both defect sites and defect electrons. As a result, the p hotoemission spectrum yields an additional shoulder at 360 nm (3.4 eV) and peaks and shoulders in the range of 500-700 nm. Electron emission from polycrystalline samples of Na+(C222Na- is strongly affected by a 7 ns pulsed Nd:YAG laser at 532 nm. The laser pulses result in transi ent depletion of shallowly trapped electrons and the creation and/or o ccupancy of defect sites. By comparing the photoemission currents befo re and after the laser pulses upon illumination at 400 and 600 nm, the energy legions of electron depletion and enhancement can be identifie d. The kinetics of photoemission decay and/or growth after the laser p ulse can be related to the competition between decay of the excess ele ctron population and photon-induced repopulation of empty traps.